Technical Field
The present invention relates to a measurement method and a measurement program. More specifically, the invention relates to a measurement method and a measurement program, for precisely measuring the surface height of a curved object.
Related Art
Light interferometry that uses brightness information of interference fringes occurring due to optical interference, has been known as a method of measuring the surface height, the surface roughness, and the three-dimensional shape of a measuring object. The light interferometry uses an increase of the brightness of interference fringes due to superposition and composition of peaks of the interference fringes between wavelengths at a focus at which the optical path length of a reference optical path and the optical path length of a measurement optical path correspond to each other. Therefore, an image pickup element, such as a CCD camera, captures an interference image indicating a two-dimensional distribution of the intensity of interference light, with the optical path length of the reference optical path or the measurement optical path, being varied, in the light interferometry. By detecting a focused position at which the intensity of the interference light has a peak at the respective measurement positions within a capturing field of view, it is possible to measure the height of a measurement surface in a corresponding measurement position and thus a three-dimensional shape or the like of the measuring object (e.g., refer to JP 2011-191118 A, JP 2015-045575 A, and JP 2015-118076 A).